$9cd + 9ce - c + 7 = -9d - 3$ Solve for $c$.
Explanation: Combine constant terms on the right. $9cd + 9ce - c + {7} = -9d - {3}$ $9cd + 9ce - c = -9d - {10}$ Notice that all the terms on the left-hand side of the equation have $c$ in them. $9{c}d + 9{c}e - 1{c} = -9d - 10$ Factor out the $c$ ${c} \cdot \left( 9d + 9e - 1 \right) = -9d - 10$ Isolate the $c$ $c \cdot \left( {9d + 9e - 1} \right) = -9d - 10$ $c = \dfrac{ -9d - 10 }{ {9d + 9e - 1} }$ We can simplify this by multiplying the top and bottom by $-1$. $c= \dfrac{9d + 10}{-9d - 9e + 1}$